My PhD work is part of a greater project called “The evolution of sex allocation and its correlates in Macrostomum”. On this project I collaborate mainly with my supervisor Lukas Schärer and my fellow PhD student Pragya Singh. To understand what the project is about I will try and unpack its title. Let’s first start with Macrostomum: Macrostomum are tiny hermaphroditic flatworms and Lukas has been studying them for more than ten years now. During that time the main focus has been on lab experiments that investigated many aspects of their morphology, mating behaviour and their life cycle. Hermaphrodites are a fascinating group of organisms to study because they can tell us more about what it means to be male or female in a biological sense. The vast majority of research into sexual conflict and sexual selection has been and still is being done with separate sexed organisms. However, hermaphroditism is quite common in nature especially among plants but also in many invertebrate groups (except for the insects for some curious reason) and therefore we should study them if we want to get a complete understanding of the dynamics that emerge from the sexes (or more precisely from anisogamy).

One of the most intriguing findings that his group has made is that worms kept in larger groups invest relatively more into the production of sperm than worms kept in small groups. This is because in pairs a worm only needs to produce enough sperm to fertilize the partner’s eggs and any additional sperm would be a waste of resources. However in larger groups it pays off for longer to produce sperm because it is likely that sperm will compete with unrelated sperm for a chance to fertilize the eggs. Lukas’s group has further found several interesting mating behaviours such as the ‘suck’ behaviour in which worms after mating put their mouth opening on top of their female genital opening and they appear to be sucking - maybe in an attempt to remove sperm. Besides the lab experiments Lukas has always had an interested in the broader taxonomy of the Macrostomorpha (the larger group Macrosotmum belongs too), but no concerted effort has been conducted so far to investigate sex allocation in a phylogenetic context. So this what the project is about. We want to measure sex allocation in many species and then try and correlate it with morphological and behavioural traits.